Method for producing feedstocks of high quality lube base oil from coking gas oil

ABSTRACT

Disclosed herein is a method of producing feedstock of high-quality lube based oil by producing coker gas oil (CGO) from vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), performing a hydrotreating process and a hydrocracking process by mixing the coker gas oil (CGO) with vacuum gas oil (VGO) to form unconverted oil (UCO), and then recycling the unconverted oil. The method of producing feedstock of high-quality lube based oil is advantageous in that feedstock of high-quality lube based oil can be more economically and efficiently produced using cheap coker gas oil (CGO), which is hard to treat.

RELATED APPLICATION

This is a §371 of International Application No. PCT/KR2008/002205, with an international filing date of Apr. 18, 2008 (WO 2009/014303 A1, published Jan. 29, 2009), which is based on Korean Patent Application No. 10-2007-0075100 filed Jul. 26, 2007.

TECHNICAL FIELD

The present disclosure relates to a method of producing feedstock of high-quality lube base oil using coker gas oil (CGO), and, more particularly, to a method of producing feedstock of high-quality lube base oil by mixing coker gas oil (CGO) with vacuum gas oil (VGO) used in a conventional hydrogenation reaction process, performing a hydrotreating process and a hydrocracking process, and then recycling the unconverted oil produced therefrom.

BACKGROUND

A conventional method of producing feedstock of lube base oil in relation to a fuel oil hydrocracking process is performed using unconverted oil (UCO), produced by hydrocracking the vacuum gas oil (VGO) produced through a vacuum distillation process (V1). In the conventional method, first, a large amount of oil is converted into light hydrocarbons through a hydrotreating (HDT)' process for removing impurities, such as sulfur, nitrogen, oxygen, metals, and the like, from oil and a hydrocracking (HDC) process, which is a main reaction process, and various cracked oils and gases are separated through a series of fractional distillation processes (Fs) to product light oil. In the reaction, the conversion rate of oil into light hydrocarbons is about 40%, and it is impossible in practice to obtain a conversion rate of 100%. Therefore, in the final fractional distillation process, since unconverted oil (UCO) always remains, some of the unconverted oil (UCO) is sent outside and then used as feedstock of lube base oil, and the remainder thereof is recycled in a hydrocracking process.

Since aromatic compounds, sulfur compounds, oxygen compounds, nitrogen compounds, etc., which are included in the supplied vacuum gas oil (VGO) in large quantities, are mostly saturated with hydrogen through a hydrotreating process, 90% or more of the concomitantly produced unconverted oil (UCO) becomes saturated hydrocarbons, thus producing oil having a high viscosity index, the viscosity index being one of the most important properties of lube base oil.

Thus, Korean Examined Patent Publication No. 96-13606, filed by the present applicant and incorporated by reference in its entirety herein, discloses a method of producing feedstock of high-quality lube base oil from unconverted oil, in which unconverted oil (UCO) is directly separated from vacuum gas oil (VGO) in a recycling mode of a fuel oil hydrocracking process and is then used as feedstock of lube base oil, so that it is not required to recycle the unconverted oil (UCO) to a first vacuum distillation process (an atmospheric residue vacuum distillation process), with the result that the loads in the first vacuum distillation process, hydrotreating process and hydrocracking process are decreased, thereby efficiently producing feedstock of high-quality lube base oil. Therefore, in the method of producing feedstock of high-quality lube base oil from unconverted oil, disclosed in this patent document, feedstock of high-quality lube base oil having a viscosity of a grade of 100N and 150N can be efficiently produced, compared to the conventional fuel oil hydrocracking process of recycling unconverted oil (UCO) to the first vacuum distillation process and hydrocracking process without using the unconverted oil (UCO) for producing feedstock of high-quality lube base oil. However, this method of producing feedstock of high-quality lube base oil from unconverted oil, disclosed in this patent document, is designed such that only vacuum gas oil (VGO) is used, and methods of more economically producing feedstock of high-quality lube base oil by recycling unconverted oil (UCO) and using cheap coker gas oil (CGO) have never been considered.

SUMMARY

Therefore, the present applicant has repeatedly conducted research on methods of more efficiently and economically producing feedstock of high-quality lube base oil. As a result, the present applicant proposed a method of producing feedstock of high-quality lube based oil by producing coker gas oil (CGO) from vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), mixing the coker gas oil (CGO) with vacuum gas oil (VGO), performing a hydrotreating process and a hydrocracking process to form unconverted oil (UCO), and then recycling the unconverted oil.

Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the prior art, and an aspect of the present disclosure is to provide a method of producing feedstock of high-quality lube based oil, in which economic efficiency can be greatly improved by utilizing cheap coker gas oil, and production efficiency can be maximized by recycling unconverted oil in a fuel oil hydrocracking process.

In order to accomplish the above, an aspect of the present disclosure provides a method of producing feedstock of high-quality lube base oil using coker gas oil (CGO), including: distilling atmospheric residue (AR) in a first vacuum distillation unit (V1) and thus separating the distilled atmospheric residue (AR) into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), and then supplying the vacuum gas oil (VGO) directly to a hydrotreating unit (HDT) and supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR) to a first fractional distillation unit (Fs1); supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), from which fuel components are separated in the first fractional distillation unit (Fs1), into a coker drum and then coking it in the coker drum, and then obtaining coker gas oil (CGO) again through the first fractional distillation unit (Fs1), and then supplying the obtained coker gas oil (CGO) into the hydrotreating unit (HDT) together with the vacuum gas oil (VGO); removing impurities from the coker gas oil (CGO) and vacuum gas oil (VGO) through the hydrotreating unit (HDT); obtaining light and heavy hydrocarbons through a hydrocracking unit (HDC); supplying the light and heavy hydrocarbons into a second fractional distillation unit (Fs2) to separate them into oil products and unconverted oil; supplying all of the separated unconverted oil into a second vacuum distillation unit (V2) to obtain feedstock of high-quality lube base oil having a predetermined viscosity grade and balanced unconverted oil; and recycling the unconverted oil obtained from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC).

Another aspect of the present disclosure provides a method of producing feedstock of high-quality lube base oil using coker gas oil (CGO), including: distilling atmospheric residue (AR) in a first vacuum distillation unit (V1) and thus separating the distilled atmospheric residue (AR) into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), and then supplying the vacuum gas oil (VGO) directly to a hydrotreating unit (HDT) and supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR) to a first fractional distillation unit (Fs1); supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), from which fuel components are separated in the first fractional distillation unit (Fs1), into a coker drum and then coking it in the coker drum, and then obtaining coker gas oil (CGO) again through the first fractional distillation unit (Fs1), and then supplying the obtained coker gas oil (CGO) into the hydrotreating unit (HDT) together with the vacuum gas oil (VGO); removing impurities from the coker gas oil (CGO) and vacuum gas oil (VGO) through the hydrotreating unit (HDT); obtaining light and heavy hydrocarbons through a hydrocracking unit (HDC); supplying the light and heavy hydrocarbons into a second fractional distillation unit (Fs2) to separate them into oil products and unconverted oil; supplying some of the separated unconverted oil into a second vacuum distillation unit (V2) to obtain feedstock of high-quality lube base oil having a predetermined viscosity grade and balanced unconverted oil; and recycling the unconverted oil separated through the second fractional distillation unit (Fs2) and the unconverted oil obtained from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC).

According to the method of producing feedstock of high-quality lube based oil of the present disclosure, the feedstock of high-quality lube based oil can be produced by producing coker gas oil (CGO) from vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), mixing the coker gas oil (CGO) with vacuum gas oil (VGO), performing a hydrotreating process and a hydrocracking process to form unconverted oil (UCO), and then recycling the unconverted oil. Therefore, the method of producing feedstock of high-quality lube based oil according to the present disclosure is advantageous in that feedstock of high-quality lube based oil can be more economically and efficiently produced using cheap coker gas oil (CGO), which is hard to treat.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic process view showing a fuel oil hydrocracking process and a process of producing feedstock of lube base oil in a recycling mode according to an exemplary embodiment of the present disclosure.

Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the attached drawings.

DETAILED DESCRIPTION

The following are descriptions of elements shown in the drawings:

CGO: coker gas oil VGO: vacuum gas oil

UCO: unconverted oil CDU: crude distillation unit

AR: atmospheric residue VR: vacuum residue

V1: first vacuum distillation unit

V2: second vacuum distillation unit

HDT: hydrotreating unit

HDC: hydrocracking unit

Fs1: first fractional distillation unit Fs2: second fractional distillation unit

As described above, FIG. 1 is a schematic process view showing a hydrocracking process using coker gas oil (CGO) supplied from a coker drum and vacuum gas oil (VGO) supplied from a first vacuum distillation unit (V1), and a method of producing feedstock of lube base oil in a recycling mode according to an exemplary embodiment of the present disclosure. In the method of producing feedstock of lube base oil, shown in FIG. 1, vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), other than vacuum gas oil (VGO), is supplied to the first fractional distillation unit (Fs1) and a coker drum and is coked in the coker drum, and is then formed into coke gas oil (CGO) through the first fractional distillation unit (Fs1) again, and then the coker gas oil (CGO) is mixed with the vacuum gas oil (VGO), and then the mixture of the coker gas oil (CGO) and the vacuum gas oil (VGO) is supplied into a hydrotreating unit and is then formed into light oil and unconverted oil (UCO) through a hydrocracking unit (HDC), thereby producing feedstock of high-quality lube base oil using the unconverted oil (UCO).

More specifically, in the method of producing feedstock of lube base oil, shown in FIG. 1, atmospheric residue (AR) separated through a crude distillation unit is distilled in a first vacuum distillation unit (V1) and is thus separated into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR). Then, the vacuum gas oil (VGO) is directly supplied to a hydrotreating unit (HDT), and the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR) is supplied to a first fractional distillation unit (Fs1). Subsequently, the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), from which fuel components have been separated in the first fractional distillation unit (Fs1), is supplied to a coker drum and is coked in the coker drum, and is then formed into coke gas oil (CGO) through the first fractional distillation unit (Fs1) again. Subsequently, the formed coke gas oil (CGO) is supplied to a hydrotreating unit (HDT) together with the vacuum gas oil (VGO).

The process of producing the coker gas oil (CGO) will be described in more detail. Components having a low boiling point are separated from the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), which is separated through the first vacuum distillation unit (V1), through the first fractional distillation unit (Fs1), and residual oil is introduced into a coker drum and is then rapidly heated to the temperature at which coke can be sufficiently formed. For this, steam is supplied into the coker drum together with the residual oil in order to maintain the minimum speed and residence time in a heater coil and prevent the formation of coke. The liquid remaining in the coker drum is converted into coke and light hydrocarbon gas, and the light hydrocarbon gas is discharged through the upper end of the coker drum. In order to perform this process, at least two coker drums are required. While coke is formed in one coker drum, in the another coker drum, the flow of oil is stopped, and coke is removed from the other coker drum. Since the coker gas oil (CGO) produced through such a coking process has poor oxidation stability and includes a large amount of HPNA (High Poly-Nuclear Aromatic hydrocarbon) having 7 or more aromatic rings, the unconverted oil, which is produced by supplying this coker gas oil (CGO) to the hydrotreating unit and hydrocracking unit, is not suitable for use as feedstock of high-quality lube base oil. However, as the method of the present disclosure, when the unconverted oil (UCO) is recycled into the hydrocracking unit (HDC), the production of high-quality unconverted oil (UCO), having good oxidation stability and including a small amount of HPNA, can be secured, feedstock of high-quality lube base oil, having a grade of 100 D to 150 D can be maximized, and the coker gas oil (CGO), having been used as conventional bunker C oil or raw material for producing diesel oil (DSL), can be used as feedstock of high-quality lube base oil, thus improving economic efficiency due to high added value.

The specific conditions in the coking process according to the exemplary method of the present disclosure are given in Table 1.

TABLE 1 Operation condition (unit) Range Heater discharge temperature (° C.) 480~500 Coker drum temperature (° C.) 500~600 Pressure of upper end of coker drum (psig) 15~30 Recycle ratio (recycle volume/supply volume) 0.05~0.2 

The coker gas oil (CGO) produced through a coking process is mixed with vacuum gas oil (VGO), and the mixture thereof is supplied into a hydrotreating unit (HDT). In this case, in the mixing of the coker gas oil (CGO) and vacuum gas oil (VGO), when the amount of the vacuum gas oil (VGO) is increased, the production amount of high-quality lube base oil is increased, but the production cost thereof is also increased. In contrast, when the amount of the coker gas oil (CGO) is increased, there is an advantage in that the production cost of the high-quality lube base oil is decreased, but there is a problem in that the material properties of the coker gas oil (CGO) are not as good as those of the vacuum gas oil (VGO), and thus it is preferred that the mixing volume ratio of the vacuum gas oil (VGO) and coker gas oil (CGO) be 3˜9. The typical material properties of the vacuum gas oil (VGO) and coker gas oil (CGO) supplied into the hydrotreating unit (HDT), and those of the unconverted oil (UCO) obtained through a hydrogenation reaction, are given in Table 2.

TABLE 2 Material properties of Products in feedstock in hydrogenation reaction hydrogenation VGO CGO feedstock reaction UCO API/Sp. Gr. 20.9/0.9285 17.8/0.9478 20.9/0.9285 39.76/0.9409 Sulfur/ 2620/16500  3120/2653  2700/1823  LT1.0/LT1.0  nitrogen, wtppm C7 insoluble 350 806 500   0.02 material, wt % Fe, wtppm   1.1 LT1.0   1.1 LT1.0 Ni, wtppm LT1.0 LT1.0 LT1.0 LT1.0 V, wtppm LT1.0 LT1.0 LT1.0 LT1.0 Distillation, ASTM D1160, @760 mmHg, ° C. Initial 274 246 274 265.1 boiling point  5% 363 354 363 379.7 10% 393 380 391 397.6 30% 429 416 426 414.5 50% 456 434 451 436.6 70% 484 453 478 464.9 90% 538 486 529 500.8 95% 569 499 554 519.8 End point 590 — 590 —

The hydrotreating unit (HDT) is a unit for removing impurities, such as sulfur, nitrogen, oxygen, metals, etc., from feedstock. The raw material passes through the hydrotreating unit (HDT), and is then converted into light hydrocarbons through a hydrocracking reaction in the hydrocracking unit (HDC) in large quantities. The hydrotreating unit (HDT) and hydrocracking unit (HDC) can be operated in a once-through mode or in a recycling mode, and can be configured in various modes, such as a one-stage mode, a two-stage mode, and the like.

The light and heavy hydrocarbons produced through the hydrocracking unit (HDC) are supplied to a second fractional distillation unit (Fs2), and are thus separated into oil products and unconverted oil (UCO). All or some of the separated unconverted oil (UCO) is supplied to a second vacuum distillation unit (V2), and thus feedstock of high-quality lube base oil having a predetermined viscosity grade is separated therefrom, and residual unconverted oil (UCO) is obtained.

Further, the residual unconverted oil (UCO), obtained from the second vacuum distillation unit (V2), is recycled into the hydrocracking unit (HDC). Meanwhile, when only some of the separated unconverted oil (UCO) is selectively supplied to the second vacuum distillation unit (V2), the residual unconverted oil (UCO) obtained from the second fractional distillation unit (Fs2) and the residual unconverted oil (UCO) obtained from the second vacuum distillation unit (V2) are simultaneously recycled into the hydrocracking unit (HDC).

In this example, it is preferred that the ratio of the unconverted oil separated through the second fractional distillation unit (Fs2) to the unconverted oil recycled into the hydrocracking unit (HDC) be 3:1˜5:1. Further, it is preferred that the ratio of the unconverted oil supplied into the second vacuum distillation unit (V2) to the unconverted oil recycled from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC) be 1.3:1˜1.5:1.

The second vacuum distillation unit (V2) is operated at a tower bottom temperature of 320˜350° C. and a tower bottom pressure of 140˜160 mmHg and at a tower top temperature of 75˜95° C. and a tower top pressure of 60˜80 mmHg, and the feedstock of lube base oil, having a predetermined viscosity grade, obtained from the second vacuum distillation unit (V2), may further be dewaxed and stabilized.

Therefore, according to the present disclosure, when atmospheric residue (AR) is supplied into the first vacuum distillation unit (V1), vacuum residue (VR) is separated through the first vacuum distillation unit (V1), coker gas oil (CGO) is extracted from the vacuum residue (VR) such that the volume of the coker gas oil is about 10˜25% of the volume of the vacuum residue (VR), the extracted coker gas oil (CGO) is mixed with the vacuum residue (VR), and the mixture thereof can be used as feedstock in the hydrotreating unit (HDT) and hydrocracking unit (HDC). Therefore, the present disclosure is advantageous in that about 10˜30% of the atmospheric residue (AR) can further be converted into high value-added light oil and feedstock of high-quality lube base oil, compared to the case where only vacuum gas oil is used as a feedstock.

Hereinafter, the present disclosure will be described in more detail with reference to the following examples for illustration purposes only, but the scope of the present disclosure is not limited thereto.

Example 1

Components having a low boiling point were separated from vacuum residue (VR), which was separated from atmospheric residue (AR) through a first vacuum distillation unit (V1), through a first fractional distillation unit (Fs1), and then the vacuum residue (VR) was heated to a temperature of 500° C. and then introduced into a coker drum. Subsequently, the vacuum residue (VR) was heated to a temperature of 550° C. at a coker drum upper end pressure of 25 Psig in the coker drum, and thus the liquid remaining in the coker drum was converted into coke and light hydrocarbon gas, and the light hydrocarbon gas was separated into LPG, Gas, naphtha, and coker gas oil (CGO) through the first fractional distillation unit (Fs1). The coker gas oil (CGO) and vacuum gas oil (VGO) having the material properties given in Table 2 were treated in a hydrotreating unit (HDT) using a catalyst (UF-210STARS, manufactured by UOP Corp.) under conditions of an LHSV (Liquid Hourly Space Velocity) of 3.429 hr⁻¹, a pressure of 2397 Psig, a temperature of 385.8° C. and a hydrogen influx rate of 842 Nm³/m³, and were then further treated together with the recycled unconverted oil (UCO), described later, in a hydrocracking unit (HDC) using a catalyst (UF-210/HC-115/UF-100, manufactured by UOP Corp.) under conditions of an LHSV of 1.241 a pressure of 2397 Psig, a temperature of 395.2° C. and a hydrogen influx rate of 1180 Nm³/m³.

Subsequently, diesel oil and light oil products having a boiling point of 350° C. or lower were recovered through a general fractional distillation process, and the unconverted oil (UCO), having the material properties given in Table 2 above, was obtained. The obtained unconverted oil (UCO) was vacuum-distilled in a UCO vacuum distillation unit (V2) at a tower top pressure of 75 mmHg and a tower top temperature of 80° C. and at a tower bottom pressure of 150 mmHg and a tower bottom temperature of 325° C., thus obtaining a light distillate in an amount of 36.3 LV %, a 100N distillate in an amount of 33.4 LV %, a middle distillate in an amount of 10.5 LV %, and a 150N distillate, which is a tower bottom product, in an amount of 19.8 LV %, as given in Table 3 below.

Among these distillates, only 100N distillate and 150N distillate were extracted from the unconverted oil (UCO) supplied into the second vacuum distillation unit (V2) such that the amount of 100N distillate and 150N distillate is 53.2% (that is, 100N: 33.4% and 150N: 19.8%) of the amount of the supplied unconverted oil (UCO), and residual unconverted oil (UCO) (46.8% of the amount of the supplied unconverted oil) was recycled into a VGO hydrocracking unit (HDC). Through these processes, 100N and 150N-grade feedstock of high-quality lube base oil having a high viscosity index and low volatility was produced, as shown in Table 3 below, and it was found that 53.2% of the unconverted oil (UCO) was recycled, so that a function for preventing fire-resistant components and poly-nuclear aromatic compounds from being accumulated was automatically accomplished, and the respective first vacuum distillation unit (V1) and hydrotreating unit (HDT) have extra capacities, with the result additional treatment capacities corresponding to the produced amount of the feedstock of lube base oil were provided, thereby very efficiently utilizing facilities.

TABLE 3 Light 100N Middle 150N distillate distillate distillate distillate API 37.6 37.3 36.7 36.0 Distillation, ASTM D1160, @760 mmHg, ° C. Initial boiling 337 398 412 438 point  5% 356 408 428 446 10% 360 411 434 452 30% 374 418 443 459 50% 381 425 459 473 70% 389 429 478 493 90% 400 445 503 529 95% 404 455 532 551 End point 411 469 533 560 Viscosity, cSt  @40° C. 19.28 @100° C. 2.968 4.28 5.065 6.751 Viscosity index 113 133 — — Flash point 210 246 (COC), ° C. Pour point, ° C. 33 39

Comparative Example

The vacuum gas oil (VGO), which was separated from atmospheric residue (AR) through a first vacuum distillation unit (V1), having the material properties given in Table 2 above, was hydrotreated in a hydrotreating unit (HDT) using a catalyst (UF-210 STARS, manufactured by UOP Corp.) under conditions of an LHSV (Liquid Hourly Space Velocity) of 3.429 hr⁻¹, a pressure of 2397 Psig, a temperature of 385.8° C. and a hydrogen influx rate of 842 Nm³/m³, and was then further treated together with the recycled unconverted oil (UCO) described later in a hydrocracking unit (HDC) using a catalyst (UF-210/HC-115/UF-100, manufactured by UOP Corp.) under the conditions of an LHSV of 1.241 hr⁻¹, a pressure of 2397 Psig, a temperature of 395.2° C. and a hydrogen influx rate of 1180 Nm³/m³.

Subsequently, diesel oil and light oil products having a boiling point of 350° C. or lower were recovered through a general separating process and several fractional distillation processes, and the unconverted oil (UCO) having the material properties given in the following Table 4 was obtained. The obtained unconverted oil (UCO) was vacuum-distilled in an UCO vacuum distillation unit (V2) at a tower top pressure of 75 mmHg and a tower top temperature of 80° C. and at a tower bottom pressure of 150 mmHg and a tower bottom temperature of 325° C., thus obtaining a light distillate in an amount of 32.5 LV %, a 100N distillate in an amount of 34.8 LV %, a middle distillate in an amount of 14.6 LV %, and a 150N distillate, which is a tower bottom product, in an amount of 18.1 LV %, as given in Table 4 below.

Among these distillates, only the 100N distillate and the 150N distillate were extracted from the unconverted oil (UCO) supplied into the second vacuum distillation unit (V2) such that the amount of 100N distillate and 150N distillate was 52.9% (that is, 100N: 34.8% and 150N: 18.1%) of the amount of the supplied unconverted oil (UCO), and residual unconverted oil (UCO) (47.1% of the amount of the supplied unconverted oil) was recycled into a hydrocracking unit (HDC). Through these processes, 100N and 150N-grade feedstock of high-quality lube base oil having a high viscosity index and low volatility was produced, as shown in Table 4 below.

TABLE 4 Light 100N Middle 150N UCO distillate distillate distillate distillate API 39.5 37.4 37.1 36.5 35.9 Distillation, ASTM D1160, @760 mmHg, ° C. Initial 276 338 401 412 437 boiling point  5% 368 358 410 428 449 10% 398 362 412 434 453 30% 432 376 418 443 461 50% 457 383 424 459 475 70% 485 392 432 478 496 90% 537 403 447 503 531 95% 567 406 456 532 552 End point 590 414 471 533 562 Viscosity, cSt @40° C. 20 19.39 @100° C. 4.428 2.978 4.305 5.065 6.787 Viscosity 136 113 132 — — index Flash point 212 250 (COC), ° C. Pour 33 39 point, ° C.

Comparing Example 1 of the present disclosure with Comparative Example of a conventional technology, the hydrocracking conditions in both Example 1 and Comparative Example are similar to each other. However, unlike the Comparative Example, in which only vacuum gas oil (VGO) is used as a feedstock, in Example 1 of the present disclosure, 10˜25% of the coker gas oil (CGO) produced from vacuum residue (VR) or a mixture (VR/AR) of vacuum residue (VR) and atmospheric residue (AR) is mixed with the vacuum gas oil (VGO) and the mixture of the coker gas oil (CGO) and vacuum gas oil (VGO) can be used as a feedstock, and the unconverted oil (UCO) formed in this manner is recycled into a hydrocracking unit (HDC), so that feedstock of lube base oil having material properties similar to those of a conventional feedstock of lube base oil can be produced, with the result that about 10˜30% of vacuum gas oil (VGO) can be replaced with the coker gas oil (CGO), compared to Comparative Example, showing a conventional technology. That is, when the production of the feedstock of lube base oil is evaluated based on the same amount of atmospheric residue (AR), in Example 1 of the present disclosure, a large amount of high value-added light oil and feedstock of high-quality lube base oil can be produced, compared to Comparative Example, showing a conventional technology.

The foregoing examples are provided merely for the purpose of explanation and are in no way to be construed as limiting. While reference to various embodiments are shown, the words used herein are words of description and illustration, rather than words of limitation. Further, although reference to particular means, materials, and embodiments are shown, there is no limitation to the particulars disclosed herein. Rather, the embodiments extend to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims. 

1-5. (canceled)
 6. A method of producing feedstock of high-quality lube base oil using coker gas oil (CGO), comprising: distilling atmospheric residue (AR) in a first vacuum distillation unit (V1) and thus separating the distilled atmospheric residue (AR) into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), and then supplying the vacuum gas oil (VGO) directly to a hydrotreating unit (HDT) and supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR) to a first fractional distillation unit (Fs1); supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), from which fuel components are separated in the first fractional distillation unit (Fs1), into a coker drum and then coking it in the coker drum, and then obtaining coker gas oil (CGO) again through the first fractional distillation unit (Fs1), and then supplying the obtained coker gas oil (CGO) into the hydrotreating unit (HDT) together with the vacuum gas oil (VGO); removing impurities from the coker gas oil (CGO) and vacuum gas oil (VGO) through the hydrotreating unit (HDT); obtaining light and heavy hydrocarbons through a hydrocracking unit (HDC); supplying the light and heavy hydrocarbons into a second fractional distillation unit (Fs2) to separate them into oil products and unconverted oil; supplying all of the separated unconverted oil into a second vacuum distillation unit (V2) to obtain feedstock of high-quality lube base oil having a predetermined viscosity grade and balanced unconverted oil; and recycling the unconverted oil obtained from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC).
 7. The method of producing feedstock of high-quality lube base oil according to claim 6, wherein a mixing volume ratio (VGO/CGO) of the vacuum gas oil (VGO) to coker gas oil (CGO), supplied into the hydrotreating unit (HDT), is 3˜9.
 8. The method of producing feedstock of high-quality lube base oil according to claim 6, wherein a ratio of the unconverted oil separated through the second fractional distillation unit (Fs2) to the unconverted oil recycled into the hydrocracking unit (HDC) is 3:1˜5:1.
 9. The method of producing feedstock of high-quality lube base oil according to claim 6, wherein a ratio of the unconverted oil supplied into the second vacuum distillation unit (V2) to the unconverted oil recycled from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC) is 1.3:1˜1.5:1.
 10. A method of producing feedstock of high-quality lube base oil using coker gas oil (CGO), comprising: distilling atmospheric residue (AR) in a first vacuum distillation unit (V1) and thus separating the distilled atmospheric residue (AR) into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), and then supplying the vacuum gas oil (VGO) directly to a hydrotreating unit (HDT) and supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR) to a first fractional distillation unit (Fs1); supplying the vacuum residue (VR) or the mixture (VR/AR) of atmospheric residue (AR) and vacuum residue (VR), from which fuel components are separated in the first fractional distillation unit (Fs1), into a coker drum and then coking it in the coker drum, and then obtaining coker gas oil (CGO) again through the first fractional distillation unit (Fs1), and then supplying the obtained coker gas oil (CGO) into the hydrotreating unit (HDT) together with the vacuum gas oil (VGO); removing impurities from the coker gas oil (CGO) and vacuum gas oil (VGO) through the hydrotreating unit (HDT); obtaining light and heavy hydrocarbons through a hydrocracking unit (HDC); supplying the light and heavy hydrocarbons into a second fractional distillation unit (Fs2) to separate them into oil products and unconverted oil; supplying a part of the separated unconverted oil into a second vacuum distillation unit (V2) to obtain feedstock of high-quality lube base oil having a predetermined viscosity grade and balanced unconverted oil; and recycling the unconverted oil separated through the second fractional distillation unit (Fs2) and the unconverted oil obtained from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC).
 11. The method of producing feedstock of high-quality lube base oil according to claim 10, wherein a mixing volume ratio (VGO/CGO) of the vacuum gas oil (VGO) to coker gas oil (CGO), supplied into the hydrotreating unit (HDT), is 3˜9.
 12. The method of producing feedstock of high-quality lube base oil according to claim 10, wherein a ratio of the unconverted oil separated through the second fractional distillation unit (Fs2) to the unconverted oil recycled into the hydrocracking unit (HDC) is 3:1˜5:1.
 13. The method of producing feedstock of high-quality lube base oil according to claim 10, wherein a ratio of the unconverted oil supplied into the second vacuum distillation unit (V2) to the unconverted oil recycled from the second vacuum distillation unit (V2) into the hydrocracking unit (HDC) is 1.3:1˜1.5:1. 